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six locks: Simplify six_relock()

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The next patch is going to move lock->seq out of lock->state. This
replaces six_relock() with a much simpler implementation based on
trylock.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-06-16 15:00:48 -04:00
parent 37f612bea5
commit dc88b65f3e
1 changed files with 5 additions and 42 deletions
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47
fs/bcachefs/six.c
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@ -409,51 +409,14 @@ EXPORT_SYMBOL_GPL(six_trylock_ip);
bool six_relock_ip(struct six_lock *lock, enum six_lock_type type,
unsigned seq, unsigned long ip)
{
const struct six_lock_vals l[] = LOCK_VALS;
u64 old, v;
if (six_lock_seq(lock) != seq || !six_trylock_ip(lock, type, ip))
return false;
EBUG_ON(type == SIX_LOCK_write);
if (type == SIX_LOCK_read &&
lock->readers) {
bool ret;
preempt_disable();
this_cpu_inc(*lock->readers);
smp_mb();
old = atomic64_read(&lock->state);
ret = !(old & l[type].lock_fail) && six_state_seq(old) == seq;
this_cpu_sub(*lock->readers, !ret);
preempt_enable();
/*
* Similar to the lock path, we may have caused a spurious write
* lock fail and need to issue a wakeup:
*/
if (ret)
six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);
else if (old & SIX_STATE_WAITING_WRITE)
six_lock_wakeup(lock, old, SIX_LOCK_write);
return ret;
if (six_lock_seq(lock) != seq) {
six_unlock_ip(lock, type, ip);
return false;
}
v = atomic64_read(&lock->state);
do {
old = v;
if ((old & l[type].lock_fail) || six_state_seq(old) != seq)
return false;
} while ((v = atomic64_cmpxchg_acquire(&lock->state,
old,
old + l[type].lock_val)) != old);
six_set_owner(lock, type, old, current);
if (type != SIX_LOCK_write)
six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);
return true;
}
EXPORT_SYMBOL_GPL(six_relock_ip);